Wednesday, June 18, 2014

Coming soon to a kitchen near you - magnets in your refrigerator. And we're not talking about slapping your kid's artwork inside the fridge next to the milk and butter.

It's the next generation of residential food and drink cooling, and it's powered by magnets. Gone will be the almost century-old unit in your kitchen that uses a heat-transfer process based on liquid refrigerants called vapor compression refrigeration. Condensers and refrigerants will be replaced with magnets and special alloys that get hot and cold based on their proximity to magnetic fields. The technology could also be used for air-conditioning.

Magnetic refrigeration, proponents say, is a rapidly approaching technology that will amount to a revolution in domestic energy use.

"It's the equivalent to a gas-powered car moving to electric - that's the kind of leap we're making in refrigeration," said Ed Vineyard, a senior researcher at the U.S. Department of Energy's Oak Ridge National Laboratory. Vineyard's Building Technologies Program has teamed up with GE to bring magnetic refrigeration to the public in around five years.

The idea behind refrigerators and air conditioners is all the same. In their broadest sense, they are heat pumps - devices that take heat energy from inside your refrigerator box or room and move it outside. Removing this energy makes the temperature go down.

In most contemporary home and commercial refrigeration systems, mechanical work compresses and expands a liquid refrigerant. The pressure drop associated with expansion lowers the temperature of the refrigerant, which then cools air blown over it by a fan into the refrigerator box or the cooled room. In magnetic refrigeration systems, the compressor is replaced with magnetic fields that interact with solid refrigerants and the water-based cooling fluid. Changing the strength of magnetic fields alters how much heat is pulled away from the refrigerator box.

Along with this refrigerator revolution comes a dramatic drop in the amount of energy you need to cool your cucumbers and cantaloupes. ORNL says magnetic refrigeration "is a promising alternative to the vapor compression systems used in today's appliances" that could theoretically drop energy consumption by 25 percent compared to current technology. Those liquid refrigerant chemicals that can be damaging to the environment and hard to recycle at the end of a refrigerator's life are also being replaced by cheaper water-based fluid.

Oak Ridge National Laboratory's Ayyoud Momen works on the team's "breadboard" prototype refrigerator-freezer: a flexible platform used to evaluate material compatibility and to analyze components including the magnet, generators, motor, pump, heat exchangers, plumbing and leakless rotating valve. Courtesy ORNL.

Developers expect the new refrigerators to cost a bit more than vapor compression models, but buyers should see savings through spending less on electricity over the long term. If the technology is adopted broadly, it could mean major electricity savings on the national scale. Besides savings from more efficient refrigerators, magnetic cooling would lower electricity use in heating, ventilation and air-conditioning equipment, which accounts for around 60 percent of the average household's energy use.

Tuesday, June 17, 2014

The treatment process in progress, using chemicals naturally abundant in wastewater to clean itself.

Using wastewater to clean itself is the premise of new Australian technology that relies on the formation of compounds called hydrotalicites, and which results in less sludge than traditional water treatment with lime. In one test, the equivalent of 20 Olympic-sized swimming pools of wastewater were treated, with final sludge reductions of up to 90 percent.

Hydrotalicites are layered crystal structures of carbonates, magnesium, and aluminum, and importantly, they can trap impurities within themselves.

By chemically manipulating these elements "naturally" present in wastewater in high concentrations, researchers at CSIRO, Australia's science agency, caused the formation of these hydrotalicites. This process occurs as the concentration of magnesium and aluminum is altered and the pH of the water raised. As the crystals form, trapped within them are numerous other waste substances – in the test case, those included radium, rare earth elements, anions and transition metals.

The resulting mixture can be easily centrifuged to separate out the sludge, which there is less of due to its higher concentration and smaller volume of water mixed in. The now-concentrated sludge can be theoretically "mined" again to recover some of the metals and minerals from the mixture. The water can be more efficiently purified further, if needed, and reused by the facility.

The wastewater sludge that remains after treated water is removed from a hydrotalcite treatment.

With the reduction in volume of sludge comes greater ease and lower costs in transporting and disposing of it.

The process is being developed for licensing by Virtual Curtain Limited.

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The American Academy of Environmental Engineering and Scientists is a not-for-profit 501(c)(6) organization serving the Environmental Engineering and Environmental Science professions by providing Board Certification to those who qualify through experience and testing. The Academy also provides training through workshops and seminars, participates in accrediting universities, publishes a periodical and other reference material, interacts with students and young professionals, sponsors a university lecture series, and rewards outstanding achievements through its international awards program.